Inorganic particles are widely used as fillers to improve mechanical and thermal properties of polymers and polymer composites. Such particles can decrease shrinkage and internal stresses during fabrication of polymer articles, increase thermal conductivity, enhance thermal stability and flame resistance, and reduce material cost. Useful inorganic particles include those of talc, calcium carbonate, mica, silica, alpha zirconium phosphates, and Kaolin clays. Conventional particles are typically microns or larger in size.
Polymer nanocomposites are polymers that contain nanofillers, i.e., fillers (particles) of nanometer dimensions. Polymer nanocomposites employing inorganic nanofillers are useful in a variety of applications because of their unique electronic, optical, and mechanical properties. Due to the physical dimensions of nanofillers, they offer very high interfacial areas, and, thus, very high interfacial interactions with the polymer matrix. The physical properties of polymer nanocomposites can be enhanced to a high degree with only a relatively small amount of nanofillers. Compared to fillers of conventional sizes, nanofillers provide enhanced physical properties to polymer composites without compromising fracture toughness and optical clarity.
The use of nanofillers in semi-crystalline polymer composites results in a new crystalline morphology and in a relatively large volume percent of interfacial or transition phase. At the same time, the relatively large surface/interface areas of nanofillers render them difficult to disperse in polymers. Further, the natural aggregation tendency of nanofillers also renders them difficult to disperse. The lack of dispersibility is an impediment to the development of polyolefin-based nanocomposites, especially those of non-polar semi-crystalline polyolefins. There are currently no commercially available non-polar nanofillers.
It would be desirable to have a process for making polyolefin nanocomposites having polar nanofillers. It would further be desirable to have a process for making nanocomposites of semi-crystalline polyolefins and polar nanofillers.